I have a quick tip for making rounded corners on photos...I created a brush shape that when used as an eraser, snips off the corners of my photos, rounding them out.
To create the brush, I filled a square image with black then made a white circle offcenter so that it intersects with two diagonal corners.Here is an example...my brush looks pretty much like the one above the "und" in the picture.
Hope that is of help!

Thanks a bunch Marisa. I've been doing this for awhile now...I love the rounded corner effect.

Before I figured out how to do it myself...I bought an action that did it!

I'm able to control the roundness better by doing it myself than with that action tho.
Not sure now where I bought the action from...but I was sure glad to have it while I
was trying to figure things out in PS...LOL!